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VIS (General)

tomohiro.yamada - 12:01 Wednesday 11 March 2020 (13470)

TypeA noise projection

I summarized transfer functions from TypeAs to DARM.

I also put noise projection of tyepA control nosie for Feb. 19th.
Since I don't follow some modifications of cryopayload controls for 3 weeks or so, they might not reflect current status.

All transfer function data can be found from the link below.

https://www.dropbox.com/sh/mpmw293of80izn3/AABT2sOnG_wYJTNXIrliph0Da?dl=0

Name "combined" means combination of some measurements since I used band-limited white noise to get high coherence.
I have measured transfer functions of Roll DoF only for ITMY. For other payloads, I asuumed same TF of ITMY.

Images attached to this report

Comments to this report:

lucia.trozzo - 17:20 Wednesday 11 March 2020 (13474)

[Ushiba, Lucia]

We used the TFs and the Yamada-kun script to make the typeA control noise projection when the best sensitivity curve has been measured:
-time: 2020/03/09 13:57 UTC
- BNS 594 Kpc

The attached plots show the control noise projection for each TypeA suspension and the total contributions.

Looking at these plots seems that @ 100 Hz, the ITMX MNL_PS control noise is limiting the sensitivity.

To reduce this re-injection of noise,we are planning to add an addition rolloff filter in the PS_MN_L control for all typeA suspensions.

Note:

The data, the script (plot.py) ans TFs are saved in:

/kagra/Dropbox/Subsystems/VIS/AutoMeasurement/TypeA/Noisebudget_py

Images attached to this comment

tomohiro.yamada - 23:10 Wednesday 11 March 2020 (13487)

> ITMX MNL_PS control noise is limiting the sensitivity.

You mean ITMY MNMNY??

Before concluding this, please also check measured TFs. TFs above, let's say, 70 Hz is not so beautiful.

Measured TFs are save in kagra>Dropbox>Subsystems>VIS>Automeasurement>TypeA>.

lucia.trozzo - 19:07 Thursday 12 March 2020 (13508)

Yamada-kun pointed out that above 70 Hz, there was no coherence in the past TFs from MN_PS_L vs DARM and for this reason the conclusion "ITMX MNL_PS control noise is limiting the sensitivity" could be not correct.

To check if these loops are really limiting the sensitivity (above 100 Hz), today I measured again these TFs and estimated again these control noise contributions.

The attached plots show the results.

-In Pic1, Pic2,Pic3 Pic4, Pic5 the amplitude, the phase and the coherence are shown:

-above 100 Hz the coherence is high

- The TFs show same behavior (see Pic5) and can be fitted as 1/f^6

-Pic6 and Pic7 show the MN_PSL control noise projection for each TypeA suspension and the total contributions.

Looking at these plots seems MNL_PS control noise is not limiting the sensitivity above 100 Hz

Note

The measurements are saved in:

/kagra/Dropbox/Subsystems/VIS/Automeasurement/TypeA/ITMX/TF/Measurements/20200312

/kagra/Dropbox/Subsystems/VIS/Automeasurement/TypeA/ETMX/TF/Measurements/20200312

/kagra/Dropbox/Subsystems/VIS/Automeasurement/TypeA/ITMY/TF/Measurements/20200312

/kagra/Dropbox/Subsystems/VIS/Automeasurement/TypeA/ETMY/TF/Measurements/20200312

Images attached to this comment